Efforts have recently been made to utilize conventional telephone RJ45 jack and plug connectors for data transmission having higher transmission frequencies than is required in voice transmission. The performance criteria for such jack and plug connectors is governed by EIA/TIA standard TSB-40 (connecting hardware specification), Category 5. One aspect of the Category 5 standard is a lower level of near end crosstalk coupling between adjacent contacts of electrical connectors.
Recently, due to higher signal transmission frequencies even more stringent performance criteria have been proposed by EIA/TIA known as Category 6. Category 6 compliant connectors will be required to handle frequency rates of approximately 200 to 250 MHZ. RJ45 connectors presently being marketed fail to meet Category 6 requirements for acceptable levels of crosstalk. An additional performance criteria known as Category 5E has been established for transmission frequencies of 100 MHZ. The acceptable levels of crosstalk are lower then that permitted under Category 5 certification. Accordingly, one aspect of the present invention is to provide an RJ45 connector that will meet or exceed the requirements of Category 5E and Category 6.
Attempts to reduce crosstalk in high frequency connector applications are well known in the art. One common approach has been to modify the connector to simulate the twisting of the signal pairs which occurred in the wiring. This is achieved by crossing over the contacts in away to balance the signals and reduce crosstalk. One such example of this method is shown in U.S. Pat. No. 5,362,257 to Neal et al.
It is known in the art that the capacitive coupling between signal pairs may result in a reduction of crosstalk between same. This relationship between capacitive coupling and reduction of crosstalk is also set forth in PCT publication W094-05092. In general, the introduction of compensatory capacitance between pairs of signals results in the introduction of crosstalk from a signal line of one signal pair to a signal line of a second signal pair which counteracts inherent crosstalk otherwise introduced between the first and second signal pairs, thereby reducing overall crosstalk present on a signal pair.
Additionally, the reduction of crosstalk between adjacent connector conductors in an RJ45 connector is known in the art. A connector having crosstalk reduction is described in U.S. Pat. No. 5,454,738 to Lim et al. and U.S. Pat. No. 5,470,244 to Lim et al. The disclosure of each of these U.S. patents is hereby incorporated by reference. These references disclose an electrical connector including a printed circuit board overlying the contacts thereof having a pair of conductive traces formed on the printed circuit board. The traces are electrically connected to select contacts of the connector. The signal paths of the selected contacts are severed and then rerouted by the traces. The traces form circuit elements which balance mutual inductances for enhanced crosstalk reduction. In addition, each of the traces on the circuit board includes a portion which is in spacial registry with one of the contacts forming a capacitive coupling between the trace and the contact.
The Lim et al. design and those designs relying on inducing capacitance have several limitations. Most notably, the introduction of pure capacitive coupling between signal paths has no significant effect on reducing crosstalk at frequencies above approximately 130 MHZ. Therefore, the designs of the prior art which rely on capacitive coupling are not suitable for Category 5E or 6 applications or those requiring even higher frequency transmission rates.
Other attempts at reducing crosstalk using capacitance are known in the art. U.S. Pat. No. 5,326,284 to Bohbot et al. discloses a wall mounted telecommunications connector including a terminal jack connected to a rigid circuit board. The jack includes contacts each having a corresponding conductor path extending on the board and ending in a terminal block. The circuit board which induces the capacitive coupling includes overlying conductive tabs which are part of the signal paths. The conductive tabs therefore may tend to create stray unwanted capacitance between the tabs and adjacently disposed signal paths. Such stray capacitance is particularly of concern for high frequency, i.e., greater than 100 MHZ, applications as is appreciated by one skilled in the art.
Accordingly, it would be desirable to provide an electrical connector which reduces crosstalk between signal lines for high frequency transmission rates.